The goal of the Yale Virology Training Program is to equip predoctoral trainees with the intellectual and research foundations necessary to become independent scientists/educators investigating the molecular biology of viruses, host responses to them, and their roles in human disease. The Virology Training Program combines rigorous research training in a highly collaborative, interactive environment with a thorough academic program of instruction in modern virology, general microbiology, immunology and related disciplines. The program offers training in virtually all aspects of viral genetics, the molecular, cellular and structural biology of viruses, as well as virus-host interactions at the cellular and organismal levels. Areas of particular strength include the structural biology of viral components, viral transformation, viral entry, trafficking and replication, and the adaptive and innate immune response to viruses, including a number of select agent pathogens of biodefense interest. As a group, the 26 Virology Program trainers have an outstanding record of research accomplishment and training and many are national or international leaders in their fields. These faculty have primary appointments in 12 different Yale departments and currently have 72 predoctoral and 120 postdoctoral trainees working in their labs. Predoctoral training leading to the Ph.D. degree involves formal course work in microbiology and/or immunology, as well as other areas of biology, research rotations, teaching, and the qualifying exam in the first two years, with dissertation research beginning late in year one and becoming the primary focus of activity after completion of the qualifying exam. Intensive training in the methods, logic, and responsible conduct of research are supplemented with a wide array of opportunities for scientific interactions. The average time to obtain the Ph.D. degree is 5.5 - 6.0 years. Extensive efforts are made by Virology trainers and Yale Graduate and Medical Schools to attract and retain trainees from diverse backgrounds, particularly under-represented minority groups. This application requests funding to support six predoctoral trainees at any one time;they are supported by this grant for a maximum of three years. Relevance: This program trains young scientists to pursue research careers focused on investigating the biology of viruses, which still plague the human population as agents of infectious diseases. Such research is expected to yield new approaches to detect and combat pathogenic viruses, and new therapies that exploit the virus life cycle for positive health benefits, such as new vaccine and gene therapy vectors, and oncolytic agents.